Inspection method, power reception device, and non-contact power supply system

Abstract

This inspection method includes: a first step for causing a battery (84) to supply a second DC power to a synchronous rectification circuit during a period in which a power reception device (80) is not receiving power and causing the synchronous rectification circuit to operate in an inverter mode under the control of a control circuit; and a second step for executing determination processing for determining that there is an abnormality when the current value of a second AC power is outside a predetermined reference range.

Description

Inspection Method, Power Receiving Device, and Contactless Power Supply System Cross - Reference to Related Applications

[0001] This application is based on Japanese Application No. 2024 - 205195 filed on November 26, 2024, the content of which is incorporated herein by reference.

[0002] This disclosure relates to an inspection method, a power receiving device, and a contactless power supply system.

[0003] In Patent Document 1, in a power receiving device for contactless power supply, in order to recycle the received alternating current, a device for short - circuiting, for example, the first diode of a diode bridge for rectifying the alternating current by a switch is disclosed.

[0004] Japanese Patent Translation of PCT International Publication No. 2013 - 535948

[0005] When a power receiving device includes a switch for circulating an alternating current as in the above - mentioned technology, this switch may fail. Note that this problem is not limited to the case where the rectifier circuit for rectifying the alternating current is a diode bridge, but is common in rectifier circuits with other circuit configurations as well.

[0006] This disclosure can be realized in the following forms.

[0007] In a first embodiment of the present disclosure, a method for inspecting a power receiving device that receives power from a power transmission device in a non-contact manner is provided. The power receiving device includes a power receiving circuit having a power receiving coil that is magnetically coupled to a power transmission coil provided by the power transmission device; a synchronous rectifier circuit that operates in a rectification mode that rectifies a first AC power supplied from the power receiving circuit when receiving power and outputs a first DC power, and an inverter mode that converts the supplied second DC power into a second AC power and supplies the converted second AC power to the power receiving circuit; and a battery to which the first DC power is supplied, which supplies the second DC power to the synchronous rectifier circuit operating in the inverter mode. The inspection method includes a first step of having the battery supply the second DC power to the synchronous rectifier circuit and operating the synchronous rectifier circuit in the inverter mode during a period when the power receiving device is not receiving power; and a second step of a determination process which determines that there is an abnormality if the current value of the second AC power is outside a predetermined reference range.

[0008] This configuration allows for testing whether or not the switching elements in the rectifier circuit are faulty.

[0009] In a second embodiment of this disclosure, a power receiving device is provided that receives power from a power transmission device in a non-contact manner. The power receiving device includes a power receiving circuit having a power receiving coil that is magnetically coupled to a power transmitting coil of the power transmitting device; a synchronous rectifier circuit that operates in a rectification mode that rectifies the first AC power supplied from the power receiving circuit when power is received and outputs a first DC power, and an inverter mode that converts the supplied second DC power into a second AC power and supplies the converted second AC power to the power receiving circuit; a battery to which the first DC power is supplied and which supplies the second DC power to the synchronous rectifier circuit operating in the inverter mode; a current sensor that detects the current value of the current flowing through the power receiving coil; and a control device. The control device performs a first step of having the battery supply the second DC power to the synchronous rectifier circuit and operating the synchronous rectifier circuit in the inverter mode during a period when the power receiving device is not receiving power; and a second step of a determination process in which it determines that there is an abnormality if the current value of the second AC power detected by the current sensor is outside a predetermined reference range.

[0010] This configuration allows for testing whether or not the switching elements in the rectifier circuit are faulty.

[0011] In a third embodiment of this disclosure, a contactless power supply system comprising a power transmission device and a power receiving device is provided. The power transmission device has a power transmission coil, and the power receiving device has a power receiving circuit having a power receiving coil that is magnetically coupled to the power transmission coil of the power transmission device, a synchronous rectifier circuit that operates in a rectification mode that rectifies the first AC power supplied from the power receiving circuit when receiving power and outputs a first DC power, and an inverter mode that converts the supplied second DC power into a second AC power and supplies the converted second AC power to the power receiving circuit, a battery to which the first DC power is supplied and which supplies the second DC power to the synchronous rectifier circuit operating in the inverter mode, a current sensor that detects the current value of the current flowing through the power receiving coil, and a control device, wherein the control device performs a first step of having the battery supply the second DC power to the synchronous rectifier circuit and operating the synchronous rectifier circuit in the inverter mode during a period when the power receiving device is not receiving power, and a second step of a determination process which determines that there is an abnormality if the current value of the second AC power detected by the current sensor is outside a predetermined reference range.

[0012] This configuration allows for testing whether or not the switching elements in the rectifier circuit are faulty.

[0013] The above-mentioned and other purposes, features and advantages of this disclosure will be further clarified by the following detailed description with reference to the attached drawings. The drawings are as follows: Figure 1 is a schematic diagram showing the configuration of a contactless power supply system; Figure 2 is a circuit diagram of the contactless power supply system; Figure 3 is a flowchart showing the procedure of the inspection process; Figure 4 is a diagram showing the relationship between frequency and coil current; Figure 5 is a simulation result of the coil current under normal and abnormal conditions; Figure 6 is a circuit diagram of the rectifier circuit of the second embodiment; Figure 7 is a circuit diagram of the rectifier circuit of the third embodiment; and Figure 8 is a circuit diagram showing another embodiment of the protective switch.

[0014] A. First Embodiment: A1. Schematic Configuration of the Contactless Power Supply System: As shown in Figure 1, the contactless power supply system 1 comprises a power transmission device 10 and a power receiving device 80. In this embodiment, the power transmission device 10 is buried under the road RS. The power receiving device 80 is mounted on a vehicle VE, which is a mobile body traveling on the road RS. While the vehicle VE is traveling, the power receiving device 80 is supplied with power from the power transmission device 10. Here, "while traveling" includes cases where the vehicle VE is moving and cases where the vehicle VE is stopped, such as at a traffic light. The vehicle VE is configured as, for example, an electric vehicle or a hybrid vehicle.

[0015] The power transmission device 10 includes a power transmission circuit 12 having a power transmission coil L1, and an AC power supply 11 that supplies power to the power transmission circuit 12. The AC power supply 11 supplies power to multiple power transmission circuits 12. The multiple power transmission coils L1 are arranged along the direction of extension of the road RS.

[0016] Furthermore, the mobile device on which the power receiving device 80 is mounted is not limited to vehicles VE traveling on road RS, but may also be, for example, an AGV (Automated Guided Vehicle) or a mobile robot. Also, the power transmission device 10 may be installed not under the road RS, but on a sidewalk adjacent to the road RS, a parking lot, or along the route where the AGV travels.

[0017] The power receiving device 80 includes a battery 84, an auxiliary battery 94, a rectifier circuit 82, a power receiving circuit 81 having a power receiving coil L2, a DC-DC converter 92, an inverter 91, a motor generator 93, an auxiliary device 95, a control device 96, and a vehicle speed sensor 97. In this embodiment, the power receiving coil L2 is located on the underside of the vehicle VE, opposite the power transmission coil L1.

[0018] A rectifier circuit 82 is connected to the power receiving circuit 81. In the power receiving state, the rectifier circuit 82 converts the AC power received by the power receiving circuit 81 into DC power, and supplies the converted DC power to the battery 84, the DC-DC converter 92, and the inverter 91.

[0019] The battery 84 is a secondary battery that is charged by the supplied DC power. The inverter 91 uses the supplied DC power to drive the motor generator 93. The motor generator 93 operates as a three-phase AC motor and generates the driving force for propulsion. In addition, the motor generator 93 operates as a generator when the vehicle VE is decelerated and regenerates power. The regenerated three-phase AC power is converted to DC power by the inverter 91 and used to charge the battery 84.

[0020] The DC-DC converter 92 steps down the DC power supplied from the rectifier circuit 82 and supplies the stepped-down DC power to the auxiliary battery 94 and the auxiliary equipment 95. The auxiliary equipment 95 includes the vehicle VE's air conditioning system, electric power steering system, headlights, turn signals, wipers and other peripheral equipment, and vehicle VE accessories. The auxiliary battery 94 is a secondary battery for powering the auxiliary equipment 95. The vehicle speed sensor 97 detects the vehicle VE's moving speed and outputs a signal indicating the detected moving speed to the control device 96.

[0021] The control device 96 controls various parts of the power receiving device 80, such as the inverter 91. The control device 96 is implemented including an ECU (engine control unit). The ECU may be implemented with a single microcontroller or with multiple microcontrollers. When multiple microcontrollers are included, for example, it may include a microcontroller that controls mechanisms related to the drive of the vehicle VE, such as the motor generator 93, and a microcontroller that controls mechanisms related to the battery 84, such as the rectifier circuit 82. Furthermore, the control device 96 may be implemented including an ECU that controls various parts and a higher-level ECU that controls multiple ECUs in a unified manner.

[0022] A microcontroller is configured as a computer, including a processor and memory. Each function is realized by the processor executing programs stored in memory.

[0023] A2. Circuit configuration of the contactless power supply system: As shown in Figure 2, the power transmission device 10 is equipped with a power transmission capacitor C1 in addition to the above configuration. The power transmission capacitor C1 is connected in series with the power transmission coil L1 to form a power transmission circuit 12. Note that in Figure 2, only one of the multiple power transmission circuits 12 connected to the AC power supply 11 is shown, and the other power transmission circuits 12 are not shown.

[0024] The AC power supply 11 applies AC power at a predetermined operating frequency to the power transmission circuit 12. In this embodiment, the operating frequency is 85 kHz. When the power transmission coil L1 and the power receiving coil L2 are magnetically coupled, the power transmission circuit 12 enters a resonant state at the operating frequency.

[0025] In addition to the above configuration, the power receiving device 80 includes two power receiving capacitors C2, a filter 88, and an SMR (system main relay) 89. The power receiving coil L2 has one end L2a and the other end L2b. A resonant circuit is formed by connecting the two power receiving capacitors C2 in series to both the one end L2a and the other end L2b of the power receiving coil L2.

[0026] In this embodiment, the rectifier circuit 82 is configured as a synchronous rectifier circuit. The rectifier circuit 82 has a plurality of leg circuits 98 and a smoothing capacitor C3. The plurality of leg circuits 98 include a first leg circuit 98a and a second leg circuit 98b. The first leg circuit 98a has a first element Q1 and a third element Q3. The second leg circuit 98b has a second element Q2 and a fourth element Q4. In this embodiment, the first element Q1, the second element Q2, the third element Q3, and the fourth element Q4 are switching elements and are realized as N-channel MOSFETs (metal-oxide-semiconductor field-effect transistors).

[0027] The rectifier circuit 82 has a first output terminal T1 and a second output terminal T2. The second output terminal T2 is a terminal that is set to a reference voltage which is ground. The drain of the first element Q1 is connected to the first output terminal T1. The third element Q3 is connected in series with the first element Q1. The drain of the second element Q2 is connected to the first output terminal T1. The fourth element Q4 is connected in series with the second element Q2.

[0028] The transmission path through which the received AC current is transmitted, connected to one end L2a of the receiving coil L2, is called the first transmission path TLa. In this embodiment, the first transmission path TLa is the transmission path from one end L2a to the connection point between the first element Q1 and the third element Q3. The transmission path through which the received AC current is transmitted, connected to the other end L2b of the receiving coil L2, is called the second transmission path TLb. In this embodiment, the second transmission path TLb is the transmission path from the other end L2b to the connection point between the second element Q2 and the fourth element Q4.

[0029] Filter 88 suppresses the passage of noise components and allows signals in the desired frequency band to pass through. In Figure 2, filter 88 is shown as a second-order filter, but other filters such as low-pass filters or band-pass filters may also be used.

[0030] The SMR 89 electrically connects the rectifier circuit 82 and the battery 84 when it is ON, and disconnects the electrical connection between the rectifier circuit 82 and the battery 84 when it is OFF. The ON state of the SMR 89 refers to the state in which the contacts of the relay built into the SMR 89 are in contact. The OFF state of the SMR 89 refers to the state in which the contacts of the relay built into the SMR 89 are not in contact. Typically, when an abnormality occurs in the power receiving device 80, the control device 96 sets the SMR 89 to the OFF state, disconnecting the electrical connection between the rectifier circuit 82 and the SMR 89. In Figure 2, a circuit configuration with two relays is shown for the SMR 89, but the circuit configuration is not limited to this. The SMR 89 may have only one relay, or it may be configured with three or more relays.

[0031] The control device 96 controls the rectifier circuit 82 using the first signal Sig1, which is a control signal input to the gates of the first element Q1, the second element Q2, the third element Q3, and the fourth element Q4. The first signal Sig1 is a PWM (Pulse Width Modulation) signal.

[0032] The rectifier circuit 82 operates in at least two modes: rectifier mode and inverter mode. Rectifier mode is a mode in which the first AC power supplied from the power receiving circuit 81 is rectified and the first DC power is output. Inverter mode is a mode in which the supplied second DC power is converted into second AC power and the converted second AC power is supplied to the power receiving circuit 81.

[0033] The method of driving the rectifier circuit 82 is generally the same in both rectification mode and inverter mode. In the rectifier circuit 82, the first element Q1 and the second element Q2, which constitute the upper arm connected to the positive terminal of the battery 84, are driven complementaryly to each other. Similarly, the third element Q3 and the fourth element Q4, which constitute the lower arm connected to the negative terminal of the battery 84, are driven complementaryly to each other. The first element Q1 and the fourth element Q4 are set to the ON state when an ON signal is input to them simultaneously, and set to the OFF state when an OFF signal is input to them simultaneously. Similarly, the second element Q2 and the third element Q3 are set to the ON state when an ON signal is input to them simultaneously, and set to the OFF state when an OFF signal is input to them simultaneously. Note that the above driving method is a typical example, and the ON and OFF periods of each element can be adjusted as appropriate.

[0034] The control device 96 controls the rectifier circuit 82 in rectification mode when power is received. In rectification mode, the rectifier circuit 82 is controlled to synchronize with the phase of the AC current received by the power receiving coil L2. As a result, the DC power output from the power receiving circuit 81 is rectified by the rectifier circuit 82 and supplied to the battery 84, which is the load. The control device 96 also drives the rectifier circuit 82 so that a constant current is input to the battery 84.

[0035] For example, when the control device 96 wants to supply power from the battery 84 to the power receiving coil L2, it controls the rectifier circuit 82 in inverter mode. When AC power is supplied to the power receiving coil L2, the power receiving coil L2 generates a magnetic field. For example, when the control device 96 wants to notify the power transmission device 10 that the power receiving device 80 has approached a position where it can receive power, it controls the rectifier circuit 82 in inverter mode. As a result, an AC current flows through the power receiving coil L2, and the power receiving coil L2 generates a magnetic field. The power transmission device 10 can detect that the power receiving device 80 has approached by detecting the magnetic field generated by the power receiving coil L2, for example, using a magnetic field sensor (not shown). In inverter mode, the control device 96 controls the rectifier circuit 82 according to predetermined driving conditions.

[0036] The power receiving device 80 further includes a current sensor 71. The current sensor 71 detects the current flowing through the power receiving coil L2 and transmits a detection signal indicating the detected current Ide, which is the detected current value, to the control device 96. In Figure 2, the current sensor 71 is positioned between the power receiving capacitor C2 and the rectifier circuit 82, but the position of the current sensor 71 is not limited to this.

[0037] In the contactless power supply system 1, contactless power is supplied to the power receiving device 80 by magnetic field resonance between the power transmission coil L1 and the power receiving coil L2.

[0038] A3. Function of the protective switch: The protective switch SWp is a switch that has the function of electrically connecting the first transmission line TLa and the second transmission line TLb. When the first transmission line TLa and the second transmission line TLb are electrically connected, a current path CA is formed between one end L2a of the receiving coil L2 and the other end L2b of the receiving coil L2 through which current flows.

[0039] In this embodiment, the third element Q3 and the fourth element Q4 function as a protective switch SWp.

[0040] In this embodiment, by setting the protective switch SWp to the ON state, the current path CA shown by the dashed arrow in Figure 2 is formed. The protective switch SWp is used to protect the circuit, for example, when an abnormality occurs in the power receiving device 80. Specifically, for example, if an abnormality occurs in which the voltage of the battery 84 is abnormally high, the SMR 89 is set to the OFF state. This cuts off the input current to the battery 84, thus protecting the battery 84. In this case, the protective switch SWp is further set to the ON state. This protects the circuit elements of the circuit preceding the battery 84. If current continues to flow to the circuit preceding the battery 84 while the SMR 89 is set to OFF, there is a risk that a voltage exceeding the rated voltage will be applied to the circuit elements of the circuit preceding the battery 84. In this regard, the circuit elements can be protected by forming the current path CA and creating a current loop.

[0041] In the above explanation, it was stated that the SMR89 is set to the off state when an abnormality occurs. However, the above explanation is only one example of operation in the event of an abnormality. The control device 96 does not only turn on the protection switch SWp when the SMR89 is set to the off state. Regardless of whether the SMR89 is in the off or on state, turning on the protection switch SWp protects the circuit preceding the battery 84.

[0042] For example, circuit elements such as protective switches SWp can experience failures such as short circuits. Therefore, the inspection method described below is used to inspect these circuit elements.

[0043] A4. Inspection Method: The control device 96 controls the power receiving device 80 by executing a control program that includes an inspection process program stored in memory. The inspection method for the power receiving device 80 is realized when the control device 96 executes the control program stored in memory. The control device 96 performs the inspection process during the period when the power receiving coil L2 is not receiving power.

[0044] There are various methods for the control device 96 to determine that it is a period during which the power receiving coil L2 is not receiving power. For example, the control device 96 acquires the position information where the power transmission device 10 is arranged and the position information of the vehicle VE, and when the position of the vehicle VE is outside the arrangement location of the power transmission device 10, it determines that it is a period during which the power receiving coil L2 is not receiving power. Also, for example, when the non-contact power supply system 1 has a communication function between the power transmission device 10 and the power receiving device 80, the control device 96 can determine that it is a period during which the power receiving coil L2 is not receiving power through communication with the power transmission device 10 or the like.

[0045] In step S10 of FIG. 3, the control device 96 sets the SMR 89 to on and operates the rectifier circuit 82 in an inverter mode according to predetermined driving conditions. The driving conditions include the driving frequency of the rectifier circuit 82 and the duty ratio of the first signal Sig1. The driving conditions are set such that when the rectifier circuit 82 that is normal without a fault is controlled according to the driving conditions, the coil current flowing through the power receiving coil L2 becomes smaller than a predetermined first reference value. Also, in step S10, the control device 96 controls the rectifier circuit 82 such that the alternating current applied to the power receiving coil L2 is in the range of one cycle or more and several cycles or less. Thereby, the magnetic field radiated from the power receiving coil L2 can be suppressed. The driving conditions are obtained through experiments or the like and stored in the memory. In the present embodiment, the first reference value is an effective current value. In the present embodiment, both the driving frequency and the duty ratio are adjusted so that the coil current flowing through the power receiving coil L2 becomes smaller than the first reference value.

[0046] As shown in FIG. 4, in the power receiving circuit 81, the current becomes maximum at the resonance frequency fr. Therefore, in step S10, the control device 96 drives the rectifier circuit 82 such that the frequency of the alternating current supplied to the power receiving circuit 81 deviates from the resonance frequency fr of the power receiving circuit 81.

[0047] Furthermore, in step S10, the control device 96 adjusts the duty ratio of the first signal Sig1 input to the power receiving circuit 81. Here, the duty ratio is the ratio of the on-period during which the on-voltage of the first signal Sig1 is output to the period of the first signal Sig1. Thereby, the coil current flowing through the power receiving coil L2 can be adjusted. Specifically, the control device 96 periodically changes the duty ratio of the first signal Sig1 with respect to time so that an alternating current flows through the power receiving coil L2. In step S10, the control device 96 outputs the first signal Sig1 having a duty ratio smaller than the duty ratio when the output current of the rectifier circuit 82 is maximized when the rectifier circuit 82 is driven in the inverter mode throughout the entire cycle.

[0048] As another embodiment, in step S10, either only the method of adjusting the driving frequency of the rectifier circuit 82 to shift the frequency of the alternating current applied to the power receiving circuit 81 from the resonance frequency of the power receiving circuit 81 or the method of adjusting the duty ratio of the first signal Sig1 to reduce the current flowing through the power receiving coil L2 may be performed.

[0049] The first reference value is set to the lower limit value of the current range flowing through the power receiving coil L2 that enables the determination in the next step S12.

[0050] In step S12, the control device 96 determines whether or not the detected current Ide is outside a predetermined reference range. The reference range is obtained through experiments or the like and is stored in advance in the memory of the control device 96. Specifically, the reference range is a range that is not less than the current lower limit value and not more than the current upper limit value. The control device 96 determines in step S12 that the detected current Ide is outside the reference range when the detected current Ide is less than the current lower limit value or greater than the current upper limit value.

[0051] In step S12, if the detected current Ide is determined to be outside the reference range, there is a high possibility that the rectifier circuit 82 is abnormal, and therefore, in step S14, the control device 96 determines that it is abnormal. Depending on the location of the abnormality in the rectifier circuit 82 and the failure mode, such as open mode or short mode, the coil current may become larger than the reference range or smaller than the reference range. After performing step S14, the control device 96 terminates this processing routine.

[0052] In step S12, if it is determined that the detected current Ide is not outside the reference range, the rectifier circuit 82 is normal, and in order to perform the next test, in step S16, the control device 96 sets the first element Q1 and the second element Q2 to OFF and sets the protection switch SWp, which is the third element Q3 and the fourth element Q4, to ON.

[0053] In step S10, an alternating current flows through the receiving coil L2, causing energy to be stored in the receiving coil L2. Then, in step S16, when the current path CA is formed, an oscillating current flows through the current path CA.

[0054] In step S18, the control device 96 measures the decay time TDd from the time step S16 is performed until the detected current Ide becomes smaller than a predetermined second reference value Is2. In this embodiment, the second reference value Is2 is the effective current value.

[0055] Figure 5 shows the simulation results of the coil current when the rectifier circuit 82 is abnormal and when it is normal. The upper part of Figure 5 shows the simulation results of the coil current when it is normal. The lower part of Figure 5 shows the simulation results of the coil current when it is abnormal. The horizontal axis in Figure 5 is time. Time t1 is the time when step S18 is performed. When the rectifier circuit 82 is normal, the equivalent load resistance is small, so the decay time TDd is relatively long. In contrast, when the rectifier circuit 82 is abnormal, the equivalent load resistance becomes large, and the decay time TDd becomes shorter than when it is normal. Therefore, if the decay time TDd is less than or equal to the first reference time TDs1, it can be determined that there is an abnormality in the rectifier circuit 82. The first reference time TDs1 is determined by experimentation or other means and stored in memory.

[0056] In step S20 of Figure 3, the control device 96 determines whether the measured decay time TDd is less than or equal to the first reference time TDs1. If, in step S20, the control device 96 determines that the decay time TDd is less than or equal to the first reference time TDs1, there is a high probability that the rectifier circuit 82 is abnormal, and in step S22, the control device 96 determines that there is an abnormality and terminates this processing routine. If, in step S20, the control device 96 determines that the decay time TDd is not less than or equal to the first reference time TDs1, there is a high probability that the rectifier circuit 82 is normal, and the control device 96 terminates this processing routine.

[0057] If the control device 96 determines that an abnormality has occurred in step S14, or if it determines that an abnormality has occurred in step S22, it prompts the user to repair the malfunction using, for example, an indicator light provided by a power receiving device 80 (not shown).

[0058] The AC power supplied from the power receiving circuit 81 to the rectifier circuit 82 when receiving power is also called the first AC power. The DC power output by the rectifier circuit 82 when receiving power is also called the first DC power. The DC power supplied from the battery 84 to the rectifier circuit 82 is also called the second DC power. The AC power output from the rectifier circuit 82 to the power receiving circuit 81 is also called the second AC power. Step S10 is also called the first step. Steps S12 and S14 are also called the second step. Step S16 is also called the third step. Steps S20 and S22 are also called the fourth step. Step S14 is also called the determination process.

[0059] The first element Q1 and the second element Q2 are also called the first switching elements. The third element Q3 and the fourth element Q4 are also called the second switching elements.

[0060] According to the first embodiment described above, the power receiving device 80 includes a power receiving circuit 81, a rectifier circuit 82, a battery 84, and the rectifier circuit 82. The rectifier circuit 82 operates in rectifier mode and inverter mode. In step S10, the control device 96 operates the rectifier circuit 82 in inverter mode. In step S12, the control device 96 determines that there is an abnormality if the detected current Ide, which is the current value of the current output from the rectifier circuit 82, is outside the reference range. As a result, the control device 96 can check whether the first element Q1 to the fourth element Q4 included in the rectifier circuit 82 are faulty.

[0061] Furthermore, in step S10, the control device 96 controls the rectifier circuit 82 according to the driving conditions. These driving conditions are set so that when the rectifier circuit 82 is in a normal state and controlled according to the driving conditions, the current value output from the rectifier circuit 82 becomes smaller than a first reference value. This makes it possible to suppress the magnetic field radiated from the power receiving coil L2.

[0062] Furthermore, in step S16, the control device 96 sets the first element Q1 and the second element Q2 to off, and sets the third element Q3 and the fourth element Q4 to on. In step S20, if the decay time TDd is less than or equal to the first reference time TDs1, the control device 96 determines in step S22 that there is an abnormality. This allows the control device 96 to check whether the first element Q1 to the fourth element Q4 included in the rectifier circuit 82 are faulty.

[0063] B. Second Embodiment: In the first embodiment, the current value of the coil current is used to determine whether or not there is an abnormality. In this embodiment, voltage is used instead of current to determine whether or not there is an abnormality, which is different from the first embodiment. In this embodiment, the differences from the first embodiment will be explained, and the same components and processing steps as in the first embodiment will be denoted by the same reference numerals, and explanations will be omitted as appropriate.

[0064] As shown in Figure 6, the rectifier circuit 182 is equipped with two voltage sensors 72 instead of the current sensor 71. Each of the two voltage sensors 72 is connected in parallel to the third element Q3 and the fourth element Q4, respectively. Each voltage sensor 72 detects the source-drain voltage of the third element Q3 or the fourth element Q4 and transmits a detection signal indicating the detected voltage to the control device 96.

[0065] In this embodiment as well, the same inspection process as in the first embodiment is performed. In step S12, the control device 96 converts the voltage value of the voltage sensor 72 into a current value and uses the converted current value as the coil current value. The conversion formula from current value to voltage value is stored in the memory of the control device 96 in advance. Similarly, in step S18, the control device 96 converts the voltage value of the voltage sensor 72 into a current value and measures the time until the converted current value becomes smaller than the second reference value Is2 as the decay time TDd.

[0066] The processing contents of steps S12 and S18 are not limited to those described above. In other embodiments, for example, in step S12, the control device 96 may compare the detected voltage with a reference range indicated by a voltage equivalent to the reference range indicated by the current in step S12, which is stored in memory beforehand. Similarly, in step S18, the control device 96 may compare the detected voltage with a reference value indicated by a voltage equivalent to the second reference value Is2.

[0067] The second embodiment described above provides the same effects as the first embodiment. Furthermore, by using a voltage sensor 72 instead of a current sensor 71, manufacturing costs can be reduced compared to the case in which a current sensor 71 is used.

[0068] C. Third Embodiment: Figure 7 shows a power receiving device 280 of the third embodiment, which includes a protective switch SWp in addition to the rectifier circuit 82. Note that the filter 88 and SMR 89 are not shown in Figure 7. The power receiving device 280 of this embodiment includes switching elements Q5 and Q6, which are protective switches SWp, in addition to the rectifier circuit 82. The same reference numerals and processing steps as in the first embodiment are used, and detailed explanations are omitted as appropriate.

[0069] As shown in Figure 7, the switching elements Q5 and Q6 are N-channel MOSFETs. The switching elements Q5 and Q6 are connected in series with each other to form a bidirectional switch SWt, with their respective sources connected. Control signals are input to the gates of the switching elements Q5 and Q6 from the control device 96. In this embodiment as well, the current path CA is formed when the switching elements Q5 and Q6 are turned on.

[0070] In this embodiment, in step S16 of the inspection process, the bidirectional switch SWt is turned on instead of controlling the rectifier circuit 82. In this embodiment as well, similar to the first embodiment, the decay time TDd changes depending on whether or not there is an abnormality in the rectifier circuit 282. Therefore, in this embodiment as well, the rectifier circuit 282 can be inspected using the decay time TDd.

[0071] In Figure 7, (C1) to (C3) show that the bidirectional switch SWt is located in different positions. In (C1), the bidirectional switch SWt is located between the power receiving coil L2 and the power receiving capacitor C2. In (C2) and (C3), the bidirectional switch SWt is located between the power receiving circuit 81 and the rectifier circuit 82.

[0072] Furthermore, if the power receiving device 80 includes a filter 86 between the power receiving circuit 81 and the rectifier circuit 82, a bidirectional switch SWt may be placed between the power receiving capacitor C2 and the filter 86, as shown in Figure 7 (C2). Alternatively, a bidirectional switch SWt may be placed between the filter 86 and the rectifier circuit 82, as shown in Figure 7 (C3).

[0073] Furthermore, when the power receiving circuit 81 is located at the lower part of the vehicle VE near the road RS, and the rectifier circuit 82 is located closer to the motor generator 93 than the power receiving circuit 81, the power receiving circuit 81 and the rectifier circuit 82 are electrically connected by relatively long wiring. In this case, the bidirectional switch SWtw may be located near the power receiving circuit 81 or near the rectifier circuit 82. For example, if the power receiving circuit 81 is unitized, the bidirectional switch SWtw may be located within this unit. For example, if the rectifier circuit 82 is unitized, the bidirectional switch SWtw may be located within this unit. Also, although Figure 7 shows an example in which the power receiving device 280 is equipped with a filter 86, the power receiving device 280 does not have to be equipped with a filter 86.

[0074] D. Other Embodiments (Circuit Configuration of the Protection Switch): In the third embodiment described above, the protection switch SWp is implemented as a bidirectional switch SWtw. In another embodiment, as shown in Figure 8, a circuit is implemented in which a rectifier circuit and a protection switch SWp, which is a MOSFET, form a current path CA. In this case as well, the current path CA is formed when the protection switch SWp is turned on. With this configuration, a current path CA that loops the AC current can be formed with a single protection switch SWp. Note that in Figure 8, the protection switch SWp is shown to be placed between the power receiving coil L2 and the power receiving capacitor C2, but the placement is not limited to this. Similar to the third embodiment, the protection switch SWp may be placed between the power receiving capacitor C2 and the rectifier circuit 82.

[0075] E. Other Embodiments: (E1) In the first embodiment described above, an inspection is performed using the coil current during the period when the rectifier circuit 82 is driven in inverter mode in step S12, and an inspection is performed using the decay time TDd. In other embodiments, only one of the two inspections may be performed.

[0076] (E2) In the first embodiment described above, in step S16, the first element Q1 and the second element Q2 are set to OFF, and the third element Q3 and the fourth element Q4, which are protection switches SWp, are set to ON. In another embodiment, an inspection may be performed using the decay time TDd when all switching elements, the first element Q1, the second element Q2, the third element Q3, and the fourth element Q4, are set to OFF. In this case, current flows through the body diode of each switching element. Therefore, for the same reasons as described above, there is a difference in the resistance of the path through which the oscillating current flows between the case where there is a fault in the rectifier circuit 82 and the case where there is no fault and it is functioning normally. For this reason, an inspection can be performed using the decay time TDd to determine whether or not there is a fault in the rectifier circuit 82.

[0077] (E3) In the first embodiment described above, the reference range, first reference value, and second reference value Is2, which are indicated by current, are effective current values. These reference values ​​are not limited to effective current values, but may be, for example, the maximum current value or the current value at a predetermined timing.

[0078] (E4) In the first embodiment described above, reference values ​​such as the reference range, the first reference value, and the second reference value Is2 are stored in the memory of the control device 96 in advance. The method for comparing the magnitude relationship between the detected current Ide and the reference value is not limited to the above embodiment. For example, a generation circuit that generates a reference current may be provided, and a comparison circuit may be used to compare the reference current generated from the generation circuit with the detected current Ide.

[0079] (E5) In each of the above embodiments, the protection switch SWp is implemented with an N-channel MOSFET. In other embodiments, the protection switch SWp may be a P-channel MOSFET, or other transistors such as IGBTs with freewheeling diodes, or thyristors or triacs. Also, in the first embodiment above, the third element Q3 and the fourth element Q4 are the protection switch SWp, but the first element Q1 and the second element Q2 may also be the protection switch SWp.

[0080] (E6) In the second embodiment described above, the voltage sensor 72 is connected to the third element Q3 and the fourth element Q4, respectively. In another embodiment, the voltage sensor 72 may be connected to the first element Q1 and the second element Q2, respectively. In yet another embodiment, the voltage sensor 72 may be connected to only one of the third element Q3 and the fourth element Q4.

[0081] (E7) In the first embodiment described above, the power transmission circuit 12 has a power transmission capacitor C1 connected in series with the power transmission coil L1, and the power receiving circuit 81 has a power receiving capacitor C2 connected in series with the power receiving coil L2, which is a so-called S-S circuit configuration. The circuit configuration of the power transmission circuit 12 and the circuit configuration of the power receiving circuit 81 are not limited to the S-S method. (a) For example, the power transmission circuit 12 may have a power transmission capacitor C1 connected in parallel with the power transmission coil L1, and the power receiving circuit 81 may have a so-called P-S circuit configuration, where the power receiving coil L2 has a power receiving capacitor C2 connected in series. (b) In addition to the power transmission capacitor C1 connected in series with the power transmission coil L1, the power receiving circuit 81 may also have a so-called P-SS circuit configuration, where a capacitor is connected in parallel with the power transmission coil L1, and each of the two power receiving capacitors C2 is connected in series with each of the ends of the power receiving coil L2. (c) The power transmission circuit 12 may also include a closed circuit in which a coil and a capacitor are connected in series. The coil in this closed circuit is positioned so as to be magnetically coupled with the receiving coil L2 when the power transmission coil L1 and the receiving coil L2 are magnetically coupled. (d) Furthermore, the capacitor in the closed circuit may be connected in parallel with the coil instead of in series. (e) The power transmission circuit 12 may also include a coil connected in series with the power transmission coil L1, as well as a capacitor connected in parallel with the coil. This coil is positioned so as to be magnetically coupled with the receiving coil L2 when the power transmission coil L1 and the receiving coil L2 are magnetically coupled.

[0082] The control devices and methods described herein may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the control devices and methods described herein may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, the control devices and methods described herein may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium.

[0083] This disclosure is not limited to the embodiments and modifications described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments and modifications corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-mentioned problems, or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

[0084] Other Embodiments: Features of the present disclosure are as follows: (Embodiment 1) A method for inspecting a power receiving device (80) that receives power from a power transmitting device (10) in a non-contact manner, wherein the power receiving device comprises: a power receiving circuit (81) having a power receiving coil (L2) that is magnetically coupled to a power transmitting coil (L1) provided by the power transmitting device; a synchronous rectifier circuit (82, 182) that operates in a rectification mode that rectifies a first AC power supplied from the power receiving circuit when receiving power and outputs a first DC power, and an inverter mode that converts the supplied second DC power into a second AC power and supplies the converted second AC power to the power receiving circuit; and a battery (84) to which the first DC power is supplied, the battery supplying the second DC power to the synchronous rectifier circuit operating in the inverter mode, wherein the inspection method comprises: a first step of having the battery supply the second DC power to the synchronous rectifier circuit and operating the synchronous rectifier circuit in the inverter mode during a period when the power receiving device is not receiving power; An inspection method comprising: a determination process, the execution of a determination process that determines an abnormality if the current value of the second AC power is outside a predetermined reference range. (Embodiment 2) An inspection method according to Embodiment 1, wherein in the first step, the synchronous rectifier circuit is controlled by predetermined driving conditions, the driving conditions include the driving frequency of the synchronous rectifier circuit and the duty cycle of a control signal input to the gate of a switching element included in the synchronous rectifier circuit, and the driving conditions are set such that when the normal synchronous rectifier circuit is controlled according to the driving conditions, the current value of the second AC power becomes smaller than a predetermined first reference value.(Embodiment 3) An inspection method according to Embodiment 1 or 2, wherein the synchronous rectifier circuit has a plurality of leg circuits (98), a first output terminal (T1) and a second output terminal (T2) that output the first DC power, the second output terminal being a terminal set to a reference voltage, each of the plurality of leg circuits has a first switching element (Q1, Q2) electrically connected to the first output terminal and a second switching element (Q3, Q4) connected in series with the first switching element, a third step of turning on either the first switching element or the second switching element of each leg circuit and turning off the other, and a fourth step of determining an abnormality if the decay time from the time the third step is performed until the current value of the second AC power becomes less than a predetermined second reference value is less than or equal to a predetermined first reference time. (Embodiment 4) An inspection method according to any one of Embodiments 1 to 3, wherein the synchronous rectifier circuit has a plurality of leg circuits (98) and a first output terminal (T1) and a second output terminal (T2) that output the first DC power, the second output terminal being a terminal set to a reference voltage, each of the plurality of leg circuits has a first switching element (Q1, Q2) electrically connected to the first output terminal and a second switching element (Q3, Q4) connected in series with the first switching element, and the power receiving device further comprises a voltage sensor (72) connected in parallel to at least one of the first switching element and the second switching element in at least one of the leg circuits of the plurality of leg circuits, and the second step is to convert the voltage value of the voltage sensor into a current value and use the converted current value as the current value of the second AC power.(Form 5) A power receiving device (80) that receives power from a power transmission device (10) in a non-contact manner, comprising: a power receiving circuit (81) having a power receiving coil (L2) that is magnetically coupled to a power transmission coil (L1) provided by the power transmission device; a synchronous rectifier circuit (82, 182) that operates in a rectification mode that rectifies the first AC power supplied from the power receiving circuit when receiving power and outputs a first DC power, and an inverter mode that converts the supplied second DC power into a second AC power and supplies the converted second AC power to the power receiving circuit; a battery (84) to which the first DC power is supplied, which supplies the second DC power to the synchronous rectifier circuit operating in the inverter mode; a current sensor (71) that detects the current value of the current flowing through the power receiving coil; and a control device (96), wherein the control device operates during periods when the power receiving device is not receiving power. A power receiving device that performs the following steps: a first step of supplying the second DC power from the battery to the synchronous rectifier circuit and operating the synchronous rectifier circuit in inverter mode; and a second step of performing a determination process, wherein if the current value of the second AC power detected by the current sensor is outside a predetermined reference range, it is determined to be abnormal. (Embodiment 6) A power receiving device according to Embodiment 5, wherein the synchronous rectifier circuit has a plurality of leg circuits (98) and a first output terminal (T1) and a second output terminal (T2) that output the first DC power, the second output terminal being a terminal set to a reference voltage, each of the plurality of leg circuits has a first switching element (Q1, Q2) electrically connected to the first output terminal and a second switching element (Q3, Q4) connected in series with the first switching element, and instead of the current sensor, a voltage sensor (72) is provided in at least one of the leg circuits of the plurality of leg circuits, connected in parallel to at least one of the first switching element and the second switching element, and the control device, in the second step, converts the voltage value of the voltage sensor into a current value and uses the converted current value as the current value of the second AC power.(Model 7) A contactless power supply system (1) comprising a power transmission device (10) and a power receiving device (80), wherein the power transmission device has a power transmission coil (L1), and the power receiving device comprises a power receiving circuit (81) having a power receiving coil (L2) that is magnetically coupled to the power transmission coil (L1) of the power transmission device, a synchronous rectifier circuit (82, 182) that operates in a rectification mode that rectifies the first AC power supplied from the power receiving circuit when receiving power and outputs a first DC power, and an inverter mode that converts the supplied second DC power into a second AC power and supplies the converted second AC power to the power receiving circuit, a battery (84) to which the first DC power is supplied, which supplies the second DC power to the synchronous rectifier circuit operating in the inverter mode, a current sensor (71) that detects the current value of the current flowing through the power receiving coil, and a control device (96), wherein the control device operates during periods when the power receiving device is not receiving power. A contactless power supply system comprising: a first step of supplying the second DC power from the battery to the synchronous rectifier circuit and operating the synchronous rectifier circuit in inverter mode; and a second step of performing a determination process in which a determination is made if the current value of the second AC power detected by the current sensor is outside a predetermined reference range.

Claims

1. A method for inspecting a power receiving device (80) that receives power from a power transmission device (10) in a non-contact manner, wherein the power receiving device comprises: a power receiving circuit (81) having a power receiving coil (L2) that is magnetically coupled to a power transmission coil (L1) provided by the power transmission device; a synchronous rectifier circuit (82, 182) that operates in a rectification mode that rectifies a first AC power supplied from the power receiving circuit when receiving power and outputs a first DC power, and an inverter mode that converts the supplied second DC power into a second AC power and supplies the converted second AC power to the power receiving circuit; and a battery (84) to which the first DC power is supplied, the battery supplying the second DC power to the synchronous rectifier circuit operating in the inverter mode, wherein the inspection method comprises: a first step of causing the battery to supply the second DC power to the synchronous rectifier circuit and causing the synchronous rectifier circuit to operate in the inverter mode during a period when the power receiving device is not receiving power; An inspection method comprising a second step of a determination process, the second step of executing a determination process that determines an abnormality if the current value of the second AC power is outside a predetermined reference range.

2. An inspection method according to claim 1, wherein in the first step, the synchronous rectifier circuit is controlled by predetermined driving conditions, the driving conditions include the driving frequency of the synchronous rectifier circuit and the duty cycle of a control signal input to the gate of a switching element included in the synchronous rectifier circuit, and the driving conditions are set such that when the normal synchronous rectifier circuit is controlled according to the driving conditions, the current value of the second AC power becomes smaller than a predetermined first reference value.

3. An inspection method according to claim 1, wherein the synchronous rectifier circuit has a plurality of leg circuits (98), a first output terminal (T1) and a second output terminal (T2) that output the first DC power, the second output terminal being a terminal set to a reference voltage, each of the plurality of leg circuits has a first switching element (Q1, Q2) electrically connected to the first output terminal and a second switching element (Q3, Q4) connected in series with the first switching element, a third step of turning on either the first switching element or the second switching element of each leg circuit and turning off the other, and a fourth step of determining an abnormality if the decay time from the time the third step is performed until the current value of the second AC power becomes less than a predetermined second reference value is less than or equal to a predetermined first reference time.

4. An inspection method according to claim 1, wherein the synchronous rectifier circuit has a plurality of leg circuits (98) and a first output terminal (T1) and a second output terminal (T2) that output the first DC power, the second output terminal being a terminal set to a reference voltage, each of the plurality of leg circuits has a first switching element (Q1, Q2) electrically connected to the first output terminal and a second switching element (Q3, Q4) connected in series with the first switching element, and the power receiving device further comprises a voltage sensor (72) connected in parallel to at least one of the first switching element and the second switching element in at least one of the leg circuits of the plurality of leg circuits, and the second step is to convert the voltage value of the voltage sensor into a current value and use the converted current value as the current value of the second AC power.

5. A power receiving device (80) that receives power from a power transmission device (10) in a non-contact manner, comprising: a power receiving circuit (81) having a power receiving coil (L2) that is magnetically coupled to a power transmission coil (L1) provided by the power transmission device; a synchronous rectifier circuit (82, 182) that operates in a rectification mode that rectifies the first AC power supplied from the power receiving circuit when receiving power and outputs a first DC power, and an inverter mode that converts the supplied second DC power into a second AC power and supplies the converted second AC power to the power receiving circuit; a battery (84) to which the first DC power is supplied and which supplies the second DC power to the synchronous rectifier circuit operating in the inverter mode; a current sensor (71) that detects the current value of the current flowing through the power receiving coil; and a control device (96), wherein the control device operates during periods when the power receiving device is not receiving power. A power receiving device that performs the following steps: a first step of supplying the second DC power from the battery to the synchronous rectifier circuit and operating the synchronous rectifier circuit in inverter mode; and a second step of performing a determination process, wherein if the current value of the second AC power detected by the current sensor is outside a predetermined reference range, it is determined to be abnormal.

6. A power receiving device according to claim 5, wherein the synchronous rectifier circuit has a plurality of leg circuits (98) and a first output terminal (T1) and a second output terminal (T2) that output the first DC power, the second output terminal being a terminal set to a reference voltage, each of the plurality of leg circuits has a first switching element (Q1, Q2) electrically connected to the first output terminal and a second switching element (Q3, Q4) connected in series with the first switching element, and instead of the current sensor, a voltage sensor (72) is provided in at least one of the leg circuits of the plurality of leg circuits, connected in parallel to at least one of the first switching element and the second switching element, and the control device, in the second step, converts the voltage value of the voltage sensor into a current value and uses the converted current value as the current value of the second AC power.

7. A contactless power supply system (1) comprising a power transmission device (10) and a power receiving device (80), wherein the power transmission device has a power transmission coil (L1), and the power receiving device has a power receiving circuit (81) having a power receiving coil (L2) that is magnetically coupled to the power transmission coil (L1) of the power transmission device, a synchronous rectifier circuit (82, 182) that operates in a rectification mode that rectifies the first AC power supplied from the power receiving circuit when receiving power and outputs a first DC power, and an inverter mode that converts the supplied second DC power into a second AC power and supplies the converted second AC power to the power receiving circuit, a battery (84) to which the first DC power is supplied, which supplies the second DC power to the synchronous rectifier circuit operating in the inverter mode, a current sensor (71) that detects the current value of the current flowing through the power receiving coil, and a control device (96), wherein the control device operates during periods when the power receiving device is not receiving power. A contactless power supply system comprising: a first step of supplying the second DC power from the battery to the synchronous rectifier circuit and operating the synchronous rectifier circuit in inverter mode; and a second step of performing a determination process in which a determination is made if the current value of the second AC power detected by the current sensor is outside a predetermined reference range.

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